Are my raisers running to hot? 350 Mag MPI 2003 [SOLVED]

Pam

On my 350 Mag MPI (2003) with dry joint, sea water cooling, the raisers gets really hot when running at cruising speed. Can´t hold my hands on them for more than four seconds.

On idle, or below 2000 rpm, the front 2/3 is quite cool and the aft 1/3 is hot but not burning hot.

The impeller pump is replaced and the pressure is strong. The manifold, spacer, raiser, elbow….. al the way out to the out drive, is without obstacles.

The engine itself is not running hot, according to the gauge.

If my recollection is correct my former boats raisers, on a V8 350 Mag (260hp, 1991), didn´t get that hot. I believe I could hold my hands on them for about nine second.

 

So……now to the Q´s:

How hot does your raisers get?

Are mine to hot or is this considered normal?

If I measure with an IR temp meter, what readings would be ok?

 

Thanks

MarkB

I had an air lock in the system after my mechanic changed the impeller. Saw water pressure doing funny things when we got it in the water first time. Felt the risers getting warm (not terribly hot), and the mechanic opened a small blue bleed valve and all this air came out, then it ran cool again.

212rowboat

There is also unequal distribution of initial water supply, so, starboard is always warmer than port.  

Pam

Mark B: Do you know whitch of the blue valves the mechanic used and is your cooling system of the same kind as mine?

MarkB

I have raw water (sea water cooled). My cooling water comes from my B3 drive. I have a 2012 350 MAG engine.  I recall there is two blue screw plugs, one at the top by the thermostat?? and another by the sea water pump. He opened both.  The top one is where the air came out. And then everything got cold.

Pam

Thanks MarkB and 212rowboat.
I have the mec. looking into that tomorrow.

If that wouldn´t help, does anyone else have any suggestions?

MarkB

Well it could be thermostat stuck closed. That is good to replace every once in a while. Easy 15 minute job.

What is your water pressure? Sometimes the raw water pump casing gets scoured. Never has happened on my pump, but others have written about it, and the only solution is to get a spacer plate kit, or replace the pump.

LaRea

Have you seen the discussions about corrosion in the the Bravo 3 water intake hose restricting the water flow?  

When I had that problem on one of my 496s, my block water temperature always stayed within spec.  It was only the exhaust temp that was too high.  Granted, you have a different engine, but it's something to consider.

Pam

The thermostat is new and we also tried without a thermostat. Same result.
The entire water pump is replaced with a new one, excellent pressure, but same result.
But, yesterday we put everything back together, boat in the water, and now my starboard raiser temp is ok (120 F) but port side it still gets to hot (190 F) at 2400 rpms.  The thermostat is ok, upends up at about 146 F.
I pulled on and off the tube that goes on the bottom of the port manifold a number of times, with the engine running, on order to flush out any obstacle, in the pipe and manifold, but only tiny flakes of rust came out.  Same result.

I had my engine restarted a number of times during yesterday at one instance the engine temp also started to raise. The temp on the thermostat housing kept climbing to at least 190 F, and the gauge also indicated the engine running hot. I turned it off. This is new. Just perfect… NOT.

I let it rest for an hour, restarted, on idle, and the engine temp started to climb once again. As the T-housing, after 60 sec reached 180 F I cranked up to 2400 rpms for about a second and the temp immediately dropped to 146 and stayed there. I know that the water in the engine probably were still hot this second time and that might have caused the temp on the T-housing to raise momentarily but I should have dropped sooner and this should have happened at every one of the other start-ups I made earlier.

1, Can I be that I have some kind of obstacle residing in the tube, from the distribution housing, feeding the T-housing that most of the time obstructs the flow to the port manifold, and aft portion of the risers, and occasionally blocks the entire thermostat?  See attached cooling chart.

2, Are there any known problems with the circulation pump or the distribution housing that might cause this?

3, Other ideas?

MarkB

Do you know if thr impeller  ever broke up in the housing? 

Pam

MarkB.
According to the PO it didn´t but I don´t know how much I can trust him. Anyway he is the second ownere so anything might have hammned prior to that.
I under stand what you are getting att and the thought have crossed my mind.

Today I started upp and lett it run on idle for a while and thermostathousing rose to more than 160 F, i crancked up to 1700 rpms for 1 sec and than down to idle. The T-house stabilised at 146 whithin 90 second.
Right after that I increased to 1700 rpms during 10 minutes, the T-housing stayed att 146 F but the port raiser started to over heat. I got back to idle and then the t-houiseing started to climb in temp whil the riser decreased. After 12 minutes the T-house reached 183 F, I then got it up to 2000rpms for just a second and back to idle, and within 90 seconds the T-house dropped to and stayed at 146F.
Prior to these tests I disconected al the hoses from the t-house and flushed it with fresh water.

Is my engine hounted?

MarkB

You increase rpm, you increase water pressure which increases flow. So maybe the pump isn't generating enough flow at idle due to a blockage or even a bad pump.

Pam

Well, the pump is new. The old one was scoured but no pieces missing on the impeller.

Pam

As it turned out LaRea were spot on.

Finally I saw that on idle the water pressure was ok but as soon as increased RPMs it almost stopped.

As I removed the tube from inside of the stern towards the impeller pump I detected the inlet was almost completely clogged. See picture.

I guess that on idle, with low water speed, the tube leading from the lower unit could still stay opened. But as the amount of water flow increased with the RPMs an increasing low pressure caused the faulty tube to collapse.

I have now installed a separate pickup through the hull, blocked off the useless inlet, and the cooling of my risers’ works like a charm. Below 100F even on cruising speed. Problem solved.

Thanks a million

rasbury

wow, would love to have those temps...I have read about this but have not seriously looked into/for on my boat, I have a 270/350 mpi. Where am I looking for this hose connection? You got a good pic, must not be buried to bad.

Michael T

Nicely done Pam and another tip of the hat to LaRea!

Handymans342

Now thats ugly

Pam

To find this connection, have a look at the red markings in the pic.
You have to unscrew the two screws (mark nr 6 in red box) The lower screw is REALLY hard to get at. Spent an hour on that one alone.

As it comes to the temps my sea water is just 68F so that gives me some help to keep it cool....... and to stay out of the water. :-)

Dream_Inn

Thanks so much for the update.  This is how we all learn something.  Glad you found it!

rasbury

68 friggin degress, that's the summer? The water here in the coldest part of the winter MAY get in the mid 70's but that's about it. I wonder if my boating season was only a few months if I would go to the expense of my Rinker.....no I don't!

rasbury

I'm trying to understand the drawings.....is this being shown with the motor out? I assume you don't have to pull the motor to get to it but is that the back side of transom?

Pam

Well, this is the worst summer in 10 years. A normal summer should give us at least 76 F in the water by now. 

Yes the drawing is as if the engine was out but no you don’t have to pull the engine. It is the back side of the transom, facing forward, inside the engine compartment. The inlet, with the infernal screws, is just (aprox 1½ inch) above and slightly to the starboard side of the drive shaft.

It’s situated underneath the steering hydraulics so it's tricky to see and even worse to reach. You have to adjust with the steering wheel in order to get the steering cylinder in the optimum position. I had to detach the hose, leading from the pump, from the hydraulic cooler’s inlet so that I could reach in from both sides when I fiddled with the tools. 

In the pic, I just remembered I had, you’ll see it in the red ring. I had the engine out during winter but didn´t give this inlet any thought. Bad call.

Best of luck. 

Michael T

Pam, since you have installed a through hull water pick-up did you install an in-line strainer that you can remove the bowl to clean weeds etc. from? I have heard that is a good idea - like on our HVACs and Generators that have through hulls as these areas can be prone to weed and debris entry.

Pam

Michael, to be honest I didn’t even though I know I should.

After weeks trying to find out why I had the heat problems I frankly didn´t have time to do it properly. Our boating season is so short so the focus was on getting the boat back in the water and at least get one week of boating during excellent boating weather.

It will definitely be a winter project.

LaRea

Thanks for posting the pictures.  I'm glad you got back in the water.  Another victory for the Rinker forum!